NOTE: This is a public document about the Mound Builders, Cahokia mounds, and North American pre-Columbian cultures. Some of it was written by me, Will Rinehart, but large sections have been cribbed from Wikipedia, papers, and other sources. Where needed, dates have been converted from Before Present (BP) to the more common practice of BC and AD.

Outline:

The earliest mounds + overview

The absolute oldest mounds in the United States seem to be LSU’s Mound B and Mound A first laid out 9700 BC to 7500 BC (article). Watson Brake, in present-day Ouachita Parish, Louisiana, probably dates to 3500 BC. But it lies on private property and has never been properly excavated. For reference, the Great Pyramids of Giza were laid down sometime between 2600 and 2500 BC. Both sites show that the pre-agricultural, pre-ceramic, indigenous cultures were complex.

The best preserved and oldest mound site is Poverty Point in Epps, Louisiana. It hit its peak around 1500 BC and covers 37 acres.

Most of the big mounds were built from 1500 BC until the last big project Cahokia in 1050 AD. Before that, there were smaller pockets of mound building but most of the best sites to visit come from one of three periods:

• The Adena Culture was active from 1500 BC to 300 BC, largely in Ohio.
• The Hopewell tradition came after that, stretching from 300 BC to 400 AD. Most of the big sites are in Ohio but the trade routes stretched from Lake Ontario all the way down to Florida. See Crystal River Archaeological State Park.
• Finally, the Mississippian cultures thrived from 800 AD to 1200 AD centered on Cahokia and the American Bottom.

It doesn’t seem as though there was a single culture or society but a widely dispersed set of populations connected by a common network of trade routes.

Maps of the various traditions

Serpent Mound (300 BC?)

I first visited Serpent Mound on the Winter Solstice of all days. Pictures below.